1. Field of the Invention
The present invention relates to a driving apparatus for driving a movable part by using an actuator connected to the movable part.
2. Description of the Background Art
A shape memory alloy (hereinbelow, also called “SMA”) has a property such that even if it is plastic-deformed by an external force at a temperature equal to or less than martensite transformation start temperature, when heated to a temperature equal to or higher than reverse transformation end temperature, the SMA regains its memorized original shape. A driving apparatus using, as an actuator, an SMA having such a property is known.
In the case of making auto image stabilization by an actuator using the SMA (hereinbelow, also called “SMA actuator”), the driving performance of cancelling out a hand shake of about at least 10 Hz is demanded.
A technique for improving the driving performance of an SMA actuator having low response is proposed in, for example, Japanese Patent Laid-open No. 2003-125590. According to the technique, by improving a phase lag by performing two or more derivative control actions in a servo control system, the response of the SMA actuator is increased.
However, in the technique of Japanese Patent Laid-open No. 2003-125590, two or more derivative control actions are performed. Consequently, noise included in a measurement signal of position or the like is also amplified, and a special filter or the like is necessary as a countermeasure. Since tuning of the derivative control is difficult, there is also a problem such that a correction according to a change in environment temperature and the like is necessary. In the case of improving the response of the SMA actuator only by improving the control system (software), various problems occur as side effects. As a result, the response cannot be properly improved.